in the context of the habitat conditions of a meromictic lake on Lubuskie Lakeland

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1 Limnological Review 4 (24) Diversity of micro- and macrophyte communities in the context of the habitat conditions of a meromictic lake on Lubuskie Lakeland Mariusz Pełechaty*, Andrzej Pukacz**, Aleksandra Pełechata*, ** * Adam Mickiewicz University, Department of Hydrobiology, Marcelińska 4, 6 81 Poznań ** Adam Mickiewicz University Europa-Universität Viadrina, Collegium Polonicum, Kościuszki 1, 69 1 Słubice Abstract: Based on field investigations carried out into mid-forest Lake Lubińskie (Lubuskie Lakeland) in July, November and December 23 a rare meromictic status was stated. Qualitative and quantitative structure with higher abundance and biomass of phytoplankton (and significant contribution of dinophytes) in the layer, and a large share of the diatom biomass in the layer emphasized the vertical differences, which are typical for meromictic lakes. Analyses of phytoplankton as well as macrophytic vegetation dominated by charophyte meadows with the contribution of a rare association of Charetum delicatulae reflect good light conditions and relatively low trophy level of the studied lake. Key words: meromictic lake, charophytes, Characeae, phytoplankton, macrophytes, trophy. Introduction Lake estimation is often based on the analysis of pelagic samples and thus concerns the mid-lake zone. However, it is worth emphasizing that the phytolittoral zone is the integral part of a lake constituting a specific buffer zone (Kłosowski, 1992 and references therein). Therefore, lake estimation concerning macrophytes and their communities (macrophytoindication) fulfil its status. Macrophytes, in contrast to phytoplankton, do not indicate short-term changes of the environment being rather indicators of established and longterm processes in the ecosystem. Communities, considered as more sensitive indicators then individual species (Matuszkiewicz, 21), are commonly applied in the lake estimation, and, more precisely, in the estimation of the quality and diversity of littoral habitats (Kłosowski, Tomaszewicz, 1984; Kłosowski, 1992; 1999; Papastergiadou, Babalonas, 1993; Kłosowski, Szańkowski, 1999; Pełechaty, 1999). The aim of the study was to characterize abiotic conditions and companying phytoplankton and macrophyte communities of a lake representing rarely observed meromictic type of lakes. Study area and methods Lake Lubińskie is localized in a mesoregion of Łagowskie Lake District (Lubuskie Lakeland, mid-western Poland, Fig. 1). The lake is placed in the middle part of a postglacial Gronowsko- Rzepińsko-Torzymska tunnel-valley (λ 14 o 54.6 φ 52 o 18.6 ) in the vicinity of Lubin to the south and Boczów to the north-east. It is an outlet,

2 21 Mariusz Pełechaty, Andrzej Pukacz, Aleksandra Pełechata postglacial lake with an area of 22.7 ha and maximal depth of 21.6 m (Jańczak, 1996). The lake is supplied with the shallow subsoil waters and springs located on the southern shores of the lake. The lake s direct drainage basin constitutes a high plain located partial catchment of the left-side tributary of the Ilanka River. Over 6% of the drainage basin is covered by areas of agricultural use, including the infrastructure of Lubin village. However, the lake is effectively isolated by surrounding belt of forest, which is particularly important since denivelation of the drainage basin is considerable , ). Each time SD, electrolytic conductivity and ph (in the layer) were determined. As a result Carlson s trophy indices (1977) TSI TP and TSI SD were accounted. In the summer season samples for the phytoplankton analyses were collected from the and layers. Qualitative and quantitative structure of phytoplankton was determined with light microscopy (Olympus BX51). The phytoplankton biomass was based on biovolume measurement (Wetzel, Likens, 1991). For the macrophyte communities identification the Braun-Blanquet s method of phytosociological relevés was applied (Fukarek, 1967). Phytosociological nomenclature followed Brzeg and Wojterska s (21) syntaxonomical system. Results Fig. 1. Localization and morphometry of Lake Lubińskie on Lubuskie Lakeland Field investigations were carried out in the year 23. Habitat conditions were determined based on the samples collected in the deepest central part of Lake Lubińskie (mid-lake) in the summer season ( ).Water samples for laboratory analyses of nutrients concentrations were collected from the layer and then analyzed due to Standard Methods in the Department of Water and Soils Analyses (Adam Mickiewicz University). Simultaneously, samples for calcium concentration and hardness determination were taken. In the deepest part of the lake thermal and oxygen vertical profiles were performed three times ( , On the basis of thermal and oxygen profiles (Fig. 2), performed in the summer stagnation period and repeated twice during autumnal overturn, a meromictic character of Lake Lubińskie was stated, with the mixing layer (mixolimnion) and non-mixing deep water layer (monimolimnion). Analysis of physical-chemical properties in the layer of the pelagial revealed in the summer season an intermediate mineralization (conductivity = 45 µs/cm), good light conditions (SD visibility = 4.5 m, TSI SD = 38.3) and alkaline character of water (ph = 8.5). Nutrient concentrations (TN =.64 mg N/l and TP =.1 mg P/l, TSI TP = 71.2) are typical for eutrophy, with nitrogen limitation (N:P = 6.8). Not only organic, but also mineral forms of nutrients were found (P-PO 4 =.24 mg PO 4 /l, N- NO 2 =.6 mg N/l). Calcium concentration amounted 61.4 mg/l and hardness 1.4 o n. The qualitative analysis of phytoplankton showed a relatively small number of taxa in Lake Lubińskie (36 in the layer and 26 in the one). The diverse chlorophyte-diatom taxa were more common with greater number of chlorophyte and diatome taxa in the layer (Fig. 3a). Both layers significantly differed from each other regarding total abundance and biomass of phytoplankton, which were higher in the waters (Figs. 3b and c). The deep water layer was dominated by diatoms regarding both the abundance and biomass. In the layer the

3 Diversity of micro- and macrophyte communities in the context of the habitat conditions contribution of particular groups of phytoplankton to the total abundance was even and the dinophytes dominated with respect to biomass. representing 4 classes: Phragmitetea australis, Potametea, Charetea fragilis oraz Fontinaletea antipyreticeae. The highest number of communities (8) represented Phragmitetea australis class. However, those communities had not significant contribution in the phytolittoral and were represented by sparse patches of poorly developed high rushes. By contrast, charophyte communities predominated in the phytolittoral area, although three communities only were found to represent Charetea fragilis class (Charetum delicatulae, Charetum fragilis, Nitellopsidetum obtusae). From amongst all macrophyte communities, Charetum delicatulae, a rare charophyte community, developed markedly and formed extensive and compact meadows growing over slopes of the lake bowl up to the depth of 4 m. Also, phytocoenoses of Fontinaletum antipyreticeae revealed significant cover of the phytolittoral, reaching the depth of 5 m. Elodeid and nymphaeid communities were poorly developed and had rather negligible contribution in the phytolittoral area, which seems to be dependent on the specific morphometric features of the studied lake. Discussion Fig. 2. Vertical variation of thermal and oxygen conditions in Lake Lubińskie The macrophyte vegetation structure of Lake Lubińskie was characteristic of the deep ribbon-like lakes, with no properly developed nymphaeid zone, represented here only by individual patches of Nymphaea alba and Nuphar lutea. The phytolittoral zonation was mostly composed of helophytes and charophyte meadows bordering directly with the rushes and the shores. The main component of charophyte meadows was Chara delicatula, concerned as a rare species. Communities dominated by Fontinalis antipyretica were also frequently observed in the shallow parts of the phytolittoral. The depth and steep slopes of the lake s bowl seem to be the main factors determining such phytolittoral structure. Phytosociological analysis performed in the macrophytic vegetation of Lake Lubińskie revealed the occurrence of macrophyte communities Lake Lubińskie represents a rarely observed meromictic type of lakes, which could be characterized not only by peculiar abiotic conditions but also by specific biocoenosis (Kraska et al., 21). Despite its eutrophic character, Lake Lubińskie might be considered as a clear-water reservoir belonging to the group of lakes with high values of SD visibility within the Lubuskie Lakeland (authors own observations). Carlsosn s (1977) TSI SD index, characteristic of mesotrophic lakes, confirms this finding. It is worth emphasizing that, in spite of values typical of eutrophic state, both the nutrient concentrations and TSI TP place the studied lake within the lakes of relatively low trophy level. It might result from the fact that in this type of lakes internal enrichment in nutrients is limited and the waters (based on which the trophy state is estimated in meromictic lakes) are not supplied with phosphorus trapped in the monimolimnion and isolated from the mixolimnion by the chemocline barrier (Kraska et al., 21).

4 212 Mariusz Pełechaty, Andrzej Pukacz, Aleksandra Pełechata Quantitative analysis of phytoplankton confirmed the distinctness of habitat conditions in the mixo- and monimolimnion, which is to be seen in the case of both the abundance and biomass. As opposite to many dimictic lakes, the phytoplankton abundance and biomass were in the studied lake distinctly lower in the deep water layer (monimolimnion), which seems to confirm literature data (Camacho et al., 22). Negligible contribution of Cyanoprokaryota as well as larger share of Bacillariophyceae in the monimolimnion, previously reported also by Kraska et al. (21), corroborate meromictic conditions in the studied lake. In general, low abundance and biomass of phytoplankton in Lake Lubińskie, despite the eutrophic concentrations of nutrients, should be emphasized. In the water layer the quantities are characteristic of oligotrophic conditions, and in the layer of the mesotrophic ones (Kawecka, Eloranta, 1992). number of taxa A number of individuals / ml B 1,2 1 C Cyanoprokaryota mg / l Chlorophyta mg / l,8,6 Bacillariophyceae Chrysophyceae,4 Xantophyceae Dinophyta,2 Euglenophyta Cryptophyta Fig. 3. Results of phytoplankton analysis in the and water layers of Lake Lubińskie: a qualitative structure, b abundance, c biomass Macrophyte vegetation, and particularly the pattern of the phytolittoral development, stresses the exceptionality of Lake Lubińskie. Poorly developed helophyte zone and a large contribution of charophyte meadows seem to be conditioned by the specific morphometric features of the studied lakes corresponding with its meromictic character. Low phytocoenotic diversity and a large share of charophyte meadows under meromictic conditions were reported by Kraska et al., (21). Charophyte species found in Lake Lubińskie as well as the communities structure might also point to good light conditions and relatively low trophy level. It concerns particularly Chara delicatula and Charetum delicatulae, whose occurrence was mainly noted from so called lobelia lakes. The extent of both the species and community was limited to the northern and eastern lakelands of Poland. Since 21 Chara delicatula and Charetum delicatulae localities have been noted in lakes of mid-western Poland (Pełechaty et al., in press and references therein). References Brzeg A., Wojterska M., 21, Zespoły roślinne Wielkopolski, ich stan poznania i zagroŝenie, In: Wojterska M. (ed.), Szata roślinna Wielkopolski i Pojezierza Po-

5 Diversity of micro- and macrophyte communities in the context of the habitat conditions łudniowopomorskiego, Przewodnik sesji terenowych 52. Zjazdu PTB, września 21, Camacho A., Vicente E., Garcia-Gil L. J., Miracle M. R., Sendra M. D., Vila X., Borrego C. M., 22, Factors determining changes in the abundance and distribution of micro-, nano- and picoplanktonic phototrophs in Lake El Tobar (Central Spain), Verh. Internat. Verein. Limnol., 28, Carlson R. E., 1977, A trophic state index for lakes. Limnol. Oceanogr. 22, Fukarek F., 1967, Fitosocjologia, Państwowe Wydawnictwa Rolnicze I Leśne. Warszawa. Jańczak J. (ed.), 1996, Atlas jezior Polski, Tom I, Jeziora Pojezierza Wielkopolskiego i Pomorskiego w granicach dorzecza Odry, IMGW, Bogucki Wydawnictwo Naukowe, Poznań. Kawecka, B., Eloranta P. V., 1992, Zarys ekologii glonów wód słodkich i środowisk lądowych, PWN Publisher, Warszawa. Kłosowski S., 1992, Ekologia i wartość wskaźnikowa zbiorowisk roślinności szuwarowej naturalnych zbiorników wód stojących, Fragmenta Floristica et Geobotanica, 37, Kłosowski S., 1999, Układy przestrzenne roślinności litoralnej a procesy sukcesyjne na przykładzie jezior eutroficznych, In: Radwan S., Kornijów R. (eds.), Problemy aktywnej ochrony ekosystemów wodnych i torfowiskowych w polskich parkach narodowych, Wydawnictwo UMCS Lublin, Kłosowski S., Szańkowski M., 1999, Habitat conditions of nymphaeid associations in Poland, Hydrobiologia, 415, Kłosowski S., Tomaszewicz H., 1984, Typhetum angustifoliae and Typhetum latifoliae as indicators of various habitats, Polish Archives of Hydrobiology, 31, Kraska M., Borysiak J., Danielak K., Domek P., Goldyn R., Joniak T., Klimaszyk P., Kujawa-Pawlaczyk J., Piotrowicz R., Radziszewska R., Romanowicz W., Szeląg-Wasielewska E., Szyper H., 21, Jeziora dystroficzne i jezioro meromiktyczne w Drawieńskim Parku Narodowym, In: Wojterska M. (ed.), Szata roślinna Wielkopolski i Pojezierza Południowopomorskiego, Przewodnik sesji terenowych 52. Zjazdu PTB, września 21, Matuszkiewicz W., 21, Przewodnik do oznaczania zbiorowisk roślinnych Polski, Wydawnictwo Naukowe PWN, Warszawa. Papastergiadou E., Babalonas D., 1993, The relationships between hydrochemical environmental factors and the aquatic macrophytic vegetation in stagnant and slow flowing waters, 2, Evaluation of plant associations indicative value, Archiv für Hydrobiologie, 9, Pełechaty M., 1999, The phytosociological characteristics and requirements of the Phragmitetum communis (Gams 1927) Schmale 1939 phytocoenoses in the lakes of the Wielkopolski National Park, Hydrobiologia, 48/49, Pełechaty M., Pukacz A., Pełechata A., in press, Cooccurrence of two stoneworts of reverse ecological spectra in the same lake ecosystem, Habitat requirements of Chara delicatula Agardh and Chara globularis Thuillier in the context of bioindication, Polish Journal of Environmental Studies. Wetzel R. G., Likens G. E., 1991, Limnological analysis, Saunders. Co., Philadelphia. Streszczenie Celem badań była charakterystyka warunków abiotycznych oraz związanych z nimi zbiorowisk fitoplanktonu i makrofitów w śródleśnym Jeziorze Lubińskim na Pojezierzu Lubuskim (ryc. 1). Wyniki badań przeprowadzonych w lipcu, a następnie listopadzie i grudniu 23 roku wykazały rzadko spotykany, meromiktyczny typ ekosystemu jeziornego z wyraźnie wyodrębnionym miksolimnionem i beztlenowym monimolimnionem (ryc. 2). Struktura jakościowa i ilościowa zbiorowisk fitoplanktonu w warstwie powierzchniowej (większa liczebność i biomasa) i naddennej (niska liczebność i biomasa) potwierdziły odrębność obu stref, typową dla stanu meromiksji (ryc. 3a c). W warstwie naddennej dominowały ilościowo i pod względem biomasy okrzemki. W warstwie powierzchniowej udział poszczególnych grup fitoplanktonu w ogólnej liczebności był równomierny, pod względem biomasy dominowały dinofity. Analiza zarówno fitoplantonu, jak i roślinności makrofitowej, zdominowanej przez łąki ramienicowe z udziałem rzadkiego zespołu Charetum delicatulae, odzwierciedlają dobre warunki świetlne w jeziorze i stosunkowo niską trofię.